The parts forming industry is one of the world's largest industries in both total revenue and employment. As a multi-billion dollar industry, even small improvements to the manufacturing process can prove to have an enormous influence on system efficiency, and thus can create tremendously beneficial financial impact.
Formed parts are generally created via molds, dies and/or by thermal shaping, wherein the use of molds remains the most widely utilized methodology. There are many methods of forming a part via a mold, such as, for exemplary purposes only, stretch-blow molding, extrusion blow molding, vacuum molding, rotary molding and injection molding. Injection molding is one of the most popular methods and, as such, is one exemplary process wherein the implementation of a variety of sensory inspection specifics have been recognized as means to increase efficiency via, for example, decreased task repetition and failure, and improved part quality.
Injection molding systems are typically used for molding plastic and some metal parts by forcing liquid or molten plastic materials or powdered metal in a plastic binder matrix into specially shaped cavities in molds typically having two separable portions, or mold halves, configured to form the desired interior mold cavity or plurality of cavities when the two mold halves are mated or positioned together, wherein the plastic or plastic binder matrix is cooled and cured therein to make a generally solid part or parts. For purposes of convenience, references herein to plastic and plastic injection molds are understood to also apply to powdered metal injection molding and other materials from which shaped parts are made by injection molding, even if they are not mentioned or described specifically.
The mold close portion of the molding process generally has two primary functions, wherein the first segment of the mold close time is essentially devoted to injecting the molten material into the cavity area or areas under pressure until proper compaction and filling is accomplished. The second segment of the mold close time is essentially dedicated to cooling the injected material until a solid phase is obtained. Thus, after liquid or molten plastic is injected into the mold and the interior mold cavity or cavities is filled, the material is allowed to cool or cure to harden into a hard plastic part or several parts, depending on the number of cavities, whereafter the two mold halves are separated to expose the hard plastic part or parts so that the part or parts can be removed from the interior mold cavity or cavities.
In most injection mold production lines, the injection molding machines operate automatically, once the desired mold is installed, in continuous repetitive cycles of closing the mold halves together, heating them, injecting liquid or molten plastic into the mold cavities, cooling to cure or harden the plastic in the mold into hard plastic parts, opening or separating the mold halves, ejecting the molded hard plastic parts, and closing the mold halves together again to mold another part or set of parts. Thus, the nature of the molding process dictates that the efficiency and optimization of system operational parameters and/or part formation is critical to high-throughput requirements.
Some prior system improvements have focused on optimization of injection pressures, whereby very high pressures facilitate injection of the liquid or molten plastic into the mold cavities to completely fill all portions of the cavities in a timely manner. Other improvements have focused on reducing the incidence of unnecessary repetitious tasks, namely, the number of strokes of the ejector apparatus necessary to dislodge a formed part from a mold. For example, through the use of machine sensory systems, the time previously required for pre-set multiple ejector cycling can be substantially eliminated and wear and tear on the ejector equipment and molds can be reduced. Technologies, such as light beam sensors, vision systems, air pressure sensors, infrared sensors, vacuum sensors, and others, have been employed to assess the open mold halves for computerized comparison to reference data relating to empty mold halves stored in memory to detect any unremoved plastic parts or residual plastic material in the mold halves. In each instance, a variety of sensory data is acquired from a target site and is analyzed by a computer according to a comparative or otherwise objective specification in order to determine the presence or absence of a part within the mold. The analysis results are reported to a controller, whereby decisions relating to the ejector system are influenced and/or directed as a result thereof.
In extremely time sensitive automatic cycling systems such as injection molding machines, even slight delays can affect the overall efficiency of the system and result in substantial increase in the cost of goods. Because each such improvement, over the course of days, weeks, and months of injection molding parts in repetitive, high volume production line operations, can significantly bear on production quantity and cost factors, it remains desirable to identify any potential avenues that may lead to an advantageous reduction in cycle time.
Presently, the length of the mold close portion of the molding processing cycle is typically accomplished through trial and error of the process cycle, sometimes following rough approximations based upon mold parameters. No effective system is available or suggested for determination of specifically optimized mold close time parameters. Because the mold close portion can represent 80% of the cycle time, for example, eight (8) seconds of a total molding process time of ten (10) seconds, a time savings of even one (1) second during the mold close portion could result in a 10% increase in production volume on a single machine.
Therefore, it is readily apparent that there is a need for a sensory system and method that can decrease complete cycle time and improve efficiency by effectively reducing the mold close portion of the molding processing cycle, thereby increasing productivity and avoiding the above-discussed disadvantages.